Influence of fibre orientation and thickness on the response of CFRP composites subjected to high velocity impact loading

In the current work, the energy absorption, ballistic limit and residual velocities for different laminate ply orientations [(0/90), (0/90/30/-60), (0/90/45/-45) and (30/-60/60/-30)] and thicknesses [2 mm and 4 mm] of woven roving carbon fiber reinforced polymer [CFRP] composites are experimentally and theoretically studied. High strain rate tensile test results are used as reference values for the theoretical studies. Using an air gun, experiments are carried out to impact the carbon/epoxy laminates by a rigid conical steel bullet of 9.5 mm diameter and mass of 8 g. The results obtained from this study indicate that the (0/90) laminates absorb more energy and also have a higher ballistic limit than other lay-up sequences while energy absorption and ballistic limit are minimum for (30/-60/60/-30) laminates. The ballistic limit and energy absorption capacity of the plates increase whereas the residual velocity of the projectile decreases with the increase in thickness for laminates of all orientations. Using an Instron universal testing machine, end-notched flexure (ENF) tests are performed to determine the mode-II fracture toughness for the carbon/epoxy composites of different orientations. These results are used in the energy calculations and the influence of the mode -II fracture toughness on the energy absorption studies is discussed.